/*

   Copyright 2001-2003  The Apache Software Foundation 

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */
package org.apache.batik.bridge;

import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.batik.ext.awt.image.ARGBChannel;
import org.apache.batik.ext.awt.image.PadMode;
import org.apache.batik.ext.awt.image.renderable.DisplacementMapRable8Bit;
import org.apache.batik.ext.awt.image.renderable.Filter;
import org.apache.batik.ext.awt.image.renderable.PadRable;
import org.apache.batik.ext.awt.image.renderable.PadRable8Bit;
import org.apache.batik.gvt.GraphicsNode;
import org.w3c.dom.Element;

/**
 * Bridge class for the &lt;feDisplacementMap> element.
 *
 * @author <a href="mailto:tkormann@apache.org">Thierry Kormann</a>
 * @version $Id$
 */
public class SVGFeDisplacementMapElementBridge
    extends AbstractSVGFilterPrimitiveElementBridge {


    /**
     * Constructs a new bridge for the &lt;feDisplacementMap> element.
     */
    public SVGFeDisplacementMapElementBridge() {}

    /**
     * Returns 'feDisplacementMap'.
     */
    public String getLocalName() {
        return SVG_FE_DISPLACEMENT_MAP_TAG;
    }

    /**
     * Creates a <tt>Filter</tt> primitive according to the specified
     * parameters.
     *
     * @param ctx the bridge context to use
     * @param filterElement the element that defines a filter
     * @param filteredElement the element that references the filter
     * @param filteredNode the graphics node to filter
     *
     * @param inputFilter the <tt>Filter</tt> that represents the current
     *        filter input if the filter chain.
     * @param filterRegion the filter area defined for the filter chain
     *        the new node will be part of.
     * @param filterMap a map where the mediator can map a name to the
     *        <tt>Filter</tt> it creates. Other <tt>FilterBridge</tt>s
     *        can then access a filter node from the filterMap if they
     *        know its name.
     */
    public Filter createFilter(BridgeContext ctx,
                               Element filterElement,
                               Element filteredElement,
                               GraphicsNode filteredNode,
                               Filter inputFilter,
                               Rectangle2D filterRegion,
                               Map filterMap) {

        // 'scale' attribute - default is 0
        float scale = convertNumber(filterElement, SVG_SCALE_ATTRIBUTE, 0, ctx);

        // 'xChannelSelector' attribute - default is 'A'
        ARGBChannel xChannelSelector = convertChannelSelector
            (filterElement, SVG_X_CHANNEL_SELECTOR_ATTRIBUTE, ARGBChannel.A,
             ctx);

        // 'yChannelSelector' attribute - default is 'A'
        ARGBChannel yChannelSelector = convertChannelSelector
            (filterElement, SVG_Y_CHANNEL_SELECTOR_ATTRIBUTE, ARGBChannel.A,
             ctx);

        // 'in' attribute
        Filter in = getIn(filterElement,
                          filteredElement,
                          filteredNode,
                          inputFilter,
                          filterMap,
                          ctx);
        if (in == null) {
            return null; // disable the filter
        }

        // 'in2' attribute - required
        Filter in2 = getIn2(filterElement,
                            filteredElement,
                            filteredNode,
                            inputFilter,
                            filterMap,
                            ctx);
        if (in2 == null) {
            return null; // disable the filter
        }

        Rectangle2D defaultRegion;
        defaultRegion = (Rectangle2D)in.getBounds2D().clone();
        defaultRegion.add(in2.getBounds2D());
        // get filter primitive chain region
        Rectangle2D primitiveRegion
            = SVGUtilities.convertFilterPrimitiveRegion(filterElement,
                                                        filteredElement,
                                                        filteredNode,
                                                        defaultRegion,
                                                        filterRegion,
                                                        ctx);

        PadRable pad
            = new PadRable8Bit(in, primitiveRegion, PadMode.ZERO_PAD);

        // build the displacement map filter
        List srcs = new ArrayList(2);
        srcs.add(pad);
        srcs.add(in2);
        Filter displacementMap = new DisplacementMapRable8Bit
            (srcs, scale, xChannelSelector, yChannelSelector);

        // handle the 'color-interpolation-filters' property
        handleColorInterpolationFilters(displacementMap, filterElement);

        PadRable filter = new PadRable8Bit
            (displacementMap, primitiveRegion, PadMode.ZERO_PAD);

        // update the filter Map
        updateFilterMap(filterElement, filter, filterMap);

        return filter;
    }

    /**
     * Returns the channel for the specified feDisplacementMap filter
     * primitive attribute, considering the specified attribute name.
     *
     * @param filterElement the feDisplacementMap filter primitive element
     * @param attrName the name of the channel attribute
     * @param ctx the BridgeContext to use for error information
     */
    protected static
        ARGBChannel convertChannelSelector(Element filterElement,
                                           String attrName,
                                           ARGBChannel defaultChannel,
                                           BridgeContext ctx) {

        String s = filterElement.getAttributeNS(null, attrName);
        if (s.length() == 0) {
            return defaultChannel;
        }
        if (SVG_A_VALUE.equals(s)) {
            return ARGBChannel.A;
        }
        if (SVG_R_VALUE.equals(s)) {
            return ARGBChannel.R;
        }
        if (SVG_G_VALUE.equals(s)) {
            return ARGBChannel.G;
        }
        if (SVG_B_VALUE.equals(s)) {
            return ARGBChannel.B;
        }
        throw new BridgeException
            (ctx, filterElement, ERR_ATTRIBUTE_VALUE_MALFORMED,
             new Object[] {attrName, s});
    }
}
